1. Field of Invention
The present invention relates generally to measuring down-hole bores and in particular to an apparatus and method for measuring well bores in line with a tool string.
2. Description of Related Art
In oilfield applications, tubular wells (boreholes or wellbores) are directionally drilled through the earth using a drilling string suspended from a drilling rig. A drilling string is a collection of assembled parts including drill pipe, drill collars, tools and the drill bit. The parts are threadably coupled together to form the drill string, with the drill bit on the distal end of the string. The drilling rig may include equipment to rotate the drilling string, or the drilling string may include a mud motor, which uses hydraulic energy from drilling fluid to turn the drill bit, independent of the drill string. The drilling fluid, also known as drilling mud, passes through the interior of the drilling string, exiting the string at the drill bit and is subsequently pumped back to the surface around the exterior of the drilling string, carrying the drill cuttings with it for treatment and disposal.
It is desirable and common practice to measure the physical properties of the wellbore during or following drilling operations. Information may be obtained about the well path and position, depth, bottom-hole location, geophysical properties of the rock, etc. This information can be used to optimize the efficiency of the wellbore placement and provide information for future well use as well as any remedial steps which must be performed on the well bore.
Measurement while drilling (MWD) components may include a variety of sensors which allow for continued drilling operation while collecting data with the sensors. It should be noted that in the art it is known to distinguish between the terms “measurement while drilling” (MWD) and “logging while drilling” (LWD) in that the MWD term generally refers to measurements relating to the progress of the drilling operation (such as the trajectory, rate of penetration, etc.), whereas LWD relates to information about the wellbore physical properties (such as the porosity of the rock, vertical seismic profile, etc.). For the purpose of the description of the present invention, “wellbore measurement” is intended to cover both classifications of sensors, without limiting the type of sensors that may be described below.
Conventional methods of wellbore measurement have included tools with multiple sensors. However, many of these tools are separate from the drill string, not permitting a fluid bypass, and thus drilling operation must be ceased and the drill string may need to be removed before such tools can be inserted for measurements to be taken. Examples of such devices with multiple sensors include CN102337884 CN202194563 and CN20241128, U.S. Pat. No. 7,6989,937 to Neidhardt, U.S. Pat. No. 4,673,890 to Copeland et al., U.S. Pat. No. 7,281,578 to Nakajima et al. And US Patent Application Publication No. 2014/0138084 to Al-Mulhem.
Applicant is aware of wall contact caliper instruments for use in a drilling string which includes a bypass passage through the tool such that the drilling operation does not need to be ceased while measurements are taken. Such devices do not detect the profile of the well bore directly, but rather detect the difference in the height between the top and bottom of the tool to measure the average diameter of the bore. Examples of such devices may be found in U.S. Pat. No. 8,024,868 to Brannigan et al.